1. Field of the Invention
The present invention relates generally to structural arrangements for supporting steering devices, and more particularly, is directed to an improvement in a structural arrangement for supporting a steering device including a steering wheel and a steering shaft coupled with the steering wheel in a cabin of a vehicle.
2. Description of the Prior Art
In a steering system of a vehicle, a steering shaft coupled at its one end with a steering wheel is usually inserted into a steering column to pass therethrough to be rotatable and the steering column is fixed to a body of the vehicle so as to constitute partially a structural arrangement for supporting a steering shaft and a steering wheel in a cabin formed in the body. Such a steering column included in the structural arrangement for supporting a steering shaft and a steering wheel is attached at its lower end and middle portions respectively to two brackets provided on an upper dash panel which forms a cowl box located in a front portion of the cabin so as to be fixed to the body, as disclosed in Japanese utility model specification published before examination under publication No. 58-111668, or attached to both a bracket extending from an upper dash panel which forms a cowl box located in a front portion of the cabin and another bracket extending from a lower dash panel which is provided for separating the cabin from an engine room so as to be fixed to the body.
A previously proposed structural arrangement for supporting a steering shaft and a steering wheel in which a steering column is attached to brackets extending respectively from upper and lower dash panels is, for example, constituted as shown in FIG. 1. In such a structural arrangement, a steering column 70 into which a steering shaft 74 coupled at its one end with a steering wheel 72 is inserted to be rotatable is provided. The middle portion of the steering column 70 is attached to an upper bracket 60 which extends from an upper dash panel 62 toward the rear portion of a cabin formed in a body and the lower portion of the steering column 70 is attached through a lower bracket 64 to a bracket 66 which extends from a lower dash panel 68 toward the rear portion of the cabin, so that the steering column 70 in its entirety is fixed to the body.
In connection with the structural arrangement for supporting a steering shaft and a steering wheel thus constituted, there has been proposed to provide a supporting bar member elongating in the direction of the width of the body with both end portions fixed respectively to right and left cowl side panels which are disposed at the right and left sides of the front portion of the cabin, respectively, for supporting the bracket extending from the upper dash panel to be coupled with the middle portion of the steering column. With such a supporting bar member, the steering column is fixed more firmly to the body.
Meanwhile, there are a number of regulations with which a vehicle must comply actually. One of these regulations is related to the amount of movement of a steering wheel toward the rear portion of a cabin in a body (hereinafter, referred to as the amount of backward movement of a steering wheel) on the occasion of clash of the vehicle. Such amount of backward movement of a steering wheel is measured with a distance of horizontal movement of the steering wheel toward the rear portion of the cabin on the occasion of a frontal clash of the vehicle, and different maximum permissible values are provided for the amount of backward movement of a steering wheel in respective countries. Each vehicle is required to satisfy the regulation providing the maximum permissible value for the amount of backward movement of a steering wheel, together with other requlations.
However, in such previously proposed structural arrangements for supporting a steering shaft and a steering wheel in the cabin as described above, since the brackets to which the middle portion and the lower portion of the steering column are attached respectively are fixed firmly to the upper and lower dash panels, respectively, it is feared that the steering column in its entirety is moved linearly toward the rear portion of the cabin due to backward movements of an engine and other parts disposed in the front portion of the body directed toward the cabin and therefore the amount of backward movement of the steering wheel is made relatively large when the vehicle comes into a head-on collision. For example, in the case of the structural arrangements shown in FIG. 1, the steering column 70 in its entirety may be moved linearly toward the rear portion of the cabin together with the lower dash panel 68 moved toward the cabin as indicated with a dot-and-dash line and a distance L of horizontal movement of the steering wheel 72 toward the rear portion of the cabin may be made relatively large when the vehicle comes into a head-on collision. This results in a problem that, in the case where the maximum permissible value for the amount of backward movement of a steering wheel is provided to be relatively small by a regulation, a vehicle which employs the previously proposed structural arrangement for supporting a steering shaft and a steering wheel cannot satisfy the regulation providing such relatively small maximum permissible value for the amount of backward movement of a steering wheel.